Erosion Wear And Dynamic Characteristic Analysis Of Centrifugal Compressor Impeller

Centrifugal compressor is a type of turbo-mechinery with rotary blades, the working medium driven by high-speed rotating blades is thrown along radial direction of the impeller. Today, the centrifugal compressor has played an irreplaceable role in gas compression, petrochemicals, energy power and other fields. However, due to production needs, the centrifugal compressor is often faced with poor working conditions, in which tiny slid particles unavoidably mix in the working medium, causing erosion wear to the blades and material loss after a long-running process, triggering impeller failures. Therefore, studying erosion of particles to the impeller, and analyzing the dynamic characteristic changes of wear-damaged impeller have a great significance to understand the law of erosion failure and protect the engineering value of the compressor.For a specific impeller material KMN, the erosion wear test was conducted using self-made sandblasting tester. The test focused on the influence rules of particle impact angles and impact speeds to impeller material KMN’s erosion behavior, obtained material impact angle function and velocity index. It is found that when impact angle increases, the erosion rate increases first and then decreases, showing plastic material erosion characteristic, and the maximum erosion angle is about 36° The erosion rate increases with impact speed, showing exponential relations, and the speed index is about 3.04.For the erosion study of actual impeller, gas-particle two phase numerical simulation method within impeller was taken. By using discrete phase model and combining material impact angle function and velocity index acquired in the test, trajectory and velocity characteristics of particles with various scales in the impeller and erosion wear to impeller’s different parts were analyzed. It is found smaller particles follows the airflow better, and the trajectory is relatively more scattered, while larger particles are more easily to flow out along the pressure face of large blades. Relative to suction sides, the wear of blade pressure sides is more significant. The bottom of trailing edge of large blade pressure surface shows the most serious wear pattern, which is consistent with the failure mode of the impeller in practical investigation.Based on the actual impeller model’s failure form and the wear pattern results of gas-particle two-phase flow simulation, three-dimensional model of damaged impeller was established with localized thinning of large blade trailing edge. Using one-way fluid-structure interaction analysis technology and finite element method, the influences of rotating centrifugal force and aerodynamic force to impeller’s mode shapes and dynamic stress distributions were analyzed, and the changes of impeller dynamic characteristics caused by blade damage were studied comprehensively. The study found that relative to aerodynamic force, centrifugal stiffening effect which causes the increase of impeller natural frequency is more obvious, and when centrifugal force exists, superposed aerodynamic force almost has no effect on impeller modal. Compared with original impeller, damaged impeller’s natural frequencies under different orders decrease slightly, but with very small magnitude change except for the vibration of umbrella type. The impeller’s some certain order natural frequencies are closed to blade excitation frequency, which is prone to resonance, and the impeller shows modal localization phenomena under specific vibration mode. When separately considering aerodynamic forces, the impeller’s overall stress amplitude is on a low level. When applying aerodynamic forces of suction surfaces and pressure surfaces to the impeller, the impeller’s maximum stress gets increased and decreased respectively. The maximum stress of large blade increases slightly because of damage, and the position which shows maximum stress has changed.